In valves, such as variable chokes, for example, which are subject to erosive conditions their orifice and valve members are commonly made of highly abrasion resistant materials, such as cemented carbide or ceramic material. These abrasion resistant materials are weak in tension and shear. These materials are generally recommended for use in structures where they can be used in compression but are not subjected to tension or shear. When used in valves any relative movement between the abrasion resistant material and the other parts of the valve should be avoided to avoid damage to the abrasion resistant parts.
The R. S. Willis U.S. Pat. No. 3,207,181 and the W. J. Baker U.S. Pat. No. 3,426,797 are examples of valves using abrasion resistant materials for valve members and orifice members. The disclosures of both of these patents suggest retaining the abrasion resistant members by press fitting them into a metal carrier. When exposed to high temperatures the difference in the coefficient of thermal expansion of steel (carrier) and the abrasion resistant material will be sufficient to cause a release of the press fit at temperatures substantially above 250.degree. F.
The J. R. Claycomb U.S. Pat. No. 4,190,073 discloses another type of valve in which one of the abrasion resistant members is retained by axially clamping it about close fitting metal members through the use of a metal bolt. At elevated tempertures the expansion of the inside fitting metal members is greater than that of the abrasion resistant member and with the expansion of the tight fitting inside members the abrasion resistant member may split or otherwise rupture or if there is sufficient clearance to avoid this problem the expansion of the bolt allows the abrasion resistant member to vibrate and ultimately shatter as a result of such vibration.